If you were to steal a chunk of source code or a binary from meta/Google, you could probably get it running inside a few weeks effort.
Sure, the binary probably depends on a lot of internal proprietary infrastructure, but also most of that infrastructure is easy to write a mock implementation of, as long as you are happy for it to be in-ram, not multi-homed and don't need it to scale to billions of users.
Most of the binaries have a standalone mode for running on a developers PC with few/no dependencies anyway.
Sure, the binary probably depends on a lot of internal proprietary infrastructure, but also most of that infrastructure is easy to write a mock implementation of, as long as you are happy for it to be in-ram, not multi-homed and don't need it to scale to billions of users.
Most of the binaries have a standalone mode for running on a developers PC with few/no dependencies anyway.